The present invention relates to an improvement in fire protection systems and more particularly, but not by way of limitation, to a lightweight fire protection arrangement for an aircraft gas turbine jet engine and to the method of providing such an arrangement.
In the construction of aircraft it is recognized that regardless of the precautions taken by a manufacturer of an aircraft and by an operator of such aircraft in commercial use, a fire hazard does occur from time to time in connection with the leakage of jet fuel. Such a fire hazard would tend to occur in the direct vicinity of an aircraft gas turbine jet engine during operation. While the present invention has immediate application to aircraft gas turbine jet engine propulsion systems, it would also be equally applicable to other applications where it is necessary or desirable to provide fire protection, such as the auxiliary power unit (APU) of an aircraft or other metal surfaces of the aircraft that could be exposed to fire from jet fuel such as in the pylon structure.
The Federal Aeronautics Agency (FAA) has established a standard identified as the Federal Airworthiness Regulation 25 (FAR 25) which requires fire protection arrangements for aircraft gas turbine jet engine enclosures (i.e. nacelles) be able to withstand a 2000.degree. F. (1204.degree. C.) for 15 minutes to preclude flame penetration to the protected metal surface where it would cause melting of such metal and other undesired consequences. One present arrangement known in the art for providing fire protection for metal surfaces associated with an aircraft jet engine provides for the bonding of a stainless steel foil layer around 0.005 inch in thickness to the metal surface to be protected by means of a suitable silicone rubber sealant. While this arrangement does meet the FAA standard, the provision of a stainless steel layer obviously adds weight and cost to an engine nacelle. Further, a stainless steel layer is very difficult to deform to meet the severe contours of the protected metal surface. Thus, a need exists for a light weight, lower cost fire protection arrangement for aircraft gas turbine jet engines that permits ease of installation and which meets the FAA requirements.
The prior art patents reveal certain protective arrangements that are of interest. For example, U.S. Pat. No. 5,484,263 is directed to a heat shield for the hot section nozzle insert of a gas turbine engine that is subjected to elevated service temperatures. The heat shield includes a barrier layer comprising nitrides or oxides that are deposited on a metal such as a nickel-base superalloy by chemical and physical vapor deposition. A reflective coating forms a reflective surface on the barrier layer and is formed of a noble metal such as platinum or gold. This heat shield is intended to reflect heat from a metal insert in an aircraft engine but is not intended to contain a fire.
U.S. Pat. No. 4,441,726 is directed to a heat and vibration resistant seal arrangement for a butterfly valve for the control of exhaust gases from diesel powered engines used to power gas pumping stations and compressor stations. The seal assembly comprises a central core member constructed of a dense resilient metal wire mesh rope, an intermediate cover layer of braided, ceramic fiber sleeving material, and an outer wrap layer of braided wire mesh. The seal assembly is intended for use only as a seal for an impinging butterfly valve member of a valve assembly subject to elevated temperatures and vibration and is not intended for fire protection for an aircraft gas turbine jet engine.
U.S. Pat. No. 5,524,846 relates to a fire protection system for the strut and wing structure of an airplane. This fire protection system includes first and second sets of metal fingers that are attached to the exhaust nozzle outer sleeve and which bear against the strut structure to maintain firewall integrity and prevent hot exhaust gases from passing forwardly into the strut structure and wing area.
Other patents such as U.S. Pat. Nos. 5,514,198; 5,489,074, and 4,037,751 disclose various thermal protection arrangements such as insulating blankets or tiles that are particularly adapted for protection of the air flow side of a space vehicle upon re-entry into the atmosphere of the earth and are not intended to provide fire protection for a fire emanating from within the space vehicle.
Thus, it is a general object of the present invention to provide a light weight, lower cost, fire protection arrangement for a metal surface of a structure associated with an aircraft gas turbine jet engine.
It is a further general object to provide an arrangement and method of easily installing such an arrangement on a metal surface of an aircraft engine nacelle component to contain a jet fuel fire for a predetermined period of time to preclude melting of the metal surface and flame penetration of such surface to injure other components of an aircraft.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and application of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawing.